Ex-situ solid electrolyte interface modification using chalcogenides for lithium metal anode

ABSTRACT

Implementations described herein generally relate to metal electrodes, more specifically lithium-containing anodes, high performance electrochemical devices, such as secondary batteries, including the aforementioned lithium-containing electrodes, and methods for fabricating the same. In one implementation, an anode electrode structure is provided. The anode electrode structure comprises a current collector comprising copper. The anode electrode structure further comprises a lithium metal film formed on the current collector. The anode electrode structure further comprises a solid electrolyte interface (SEI) film stack formed on the lithium metal film. The SEI film stack comprises a chalcogenide film formed on the lithium metal film. In one implementation, the SEI film stack further comprises a lithium oxide film formed on the chalcogenide film. In one implementation, the SEI film stack further comprises a lithium carbonate film formed on the lithium oxide film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/150,111, filed Oct. 2, 2018, which claims benefit of U.S. ProvisionalPatent Application Ser. No. 62/583,911, filed Nov. 9, 2017, which isincorporated herein by reference in its entirety.

BACKGROUND Field

Implementations described herein generally relate to metal electrodes,more specifically lithium-containing anodes, high performanceelectrochemical devices, such as secondary batteries, including theaforementioned lithium-containing electrodes, and methods forfabricating the same.

Description of the Related Art

Rechargeable electrochemical storage systems are increasing inimportance for many fields of everyday life. High-capacity energystorage devices, such as lithium-ion (Li-ion) batteries and capacitors,are used in a growing number of applications, including portableelectronics, medical, transportation, grid-connected large energystorage, renewable energy storage, and uninterruptible power supply(UPS). In each of these applications, the charge/discharge time andcapacity of energy storage devices are key parameters. In addition, thesize, weight, and/or cost of such energy storage devices are also keyparameters. Further, low internal resistance is integral for highperformance. The lower the resistance, the less restriction the energystorage device encounters in delivering electrical energy. For example,in the case of a battery, internal resistance affects performance byreducing the total amount of useful energy stored by the battery as wellas the ability of the battery to deliver high current.

Li-ion batteries are thought to have the best chance at achieving thesought after capacity and cycling. However, Li-ion batteries ascurrently constituted often lack the energy capacity and number ofcharge/discharge cycles for these growing applications.

Accordingly, there is a need in the art for faster charging, highercapacity energy storage devices that have improved cycling, and can bemore cost effectively manufactured. There is also a need for componentsfor an energy storage device that reduce the internal resistance of thestorage device.

SUMMARY

Implementations described herein generally relate to metal electrodes,more specifically lithium-containing anodes, high performanceelectrochemical devices, such as secondary batteries, including theaforementioned lithium-containing electrodes, and methods forfabricating the same. In one implementation, an anode electrodestructure is provided. The anode electrode structure comprises a currentcollector comprising copper. In one implementation, the anode structurecomprises a copper film. The anode electrode structure further comprisesa lithium metal film formed on the current collector. The anodeelectrode structure further comprises a solid electrolyte interface(SEI) film stack formed on the lithium metal film. The SEI film stackcomprises a chalcogenide film formed on the lithium metal film. In oneimplementation, the SEI film stack further comprises a lithium oxidefilm formed on the chalcogenide film. In one implementation, the SEIfilm stack further comprises a lithium carbonate film formed on thelithium oxide film. In another implementation, the SEI film stackfurther comprises lithium fluoride formed on the chalcogenide film.

In another implementation, an anode electrode structure is provided. Theanode electrode structure comprises a current collector comprisingcopper. The anode electrode structure further comprises a lithium metalfilm formed on the current collector. The anode electrode structurefurther comprises a solid electrolyte interface (SEI) film stack formedon the lithium metal film. The SEI film stack comprises a lithium oxidefilm, a lithium carbonate film formed on the lithium oxide film, and achalcogenide film formed on the lithium carbonate film. In oneimplementation, the SEI film stack further comprises a lithium nitridefilm formed between the lithium metal film and the lithium oxide film.

In another implementation, a method is provided. The method comprisesforming a lithium metal film on a current collector, wherein the currentcollector comprises copper. The method further comprises forming a SEIfilm stack on the lithium metal film. Forming the SEI film stackcomprises forming a chalcogenide film on the lithium metal film, whereinthe chalcogenide film is selected from the group of bismuthchalcogenide, a copper chalcogenide, and combinations thereof. In oneimplementation, the SEI film stack further comprises at least one of alithium fluoride (LiF) film, a lithium carbonate (Li₂CO₃) film, alithium oxide film, a lithium nitride (Li₃N) film, and combinationsthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 illustrates a schematic cross-sectional view of oneimplementation of an energy storage device incorporating an electrodestructure having a solid electrolyte interphase (SEI) film stack formedaccording to implementations described herein;

FIG. 2 illustrates a cross-sectional view of one implementation of adual-sided anode electrode structure having a solid electrolyteinterphase (SEI) film stack formed according to implementationsdescribed herein;

FIG. 3 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure having a solid electrolyteinterphase (SEI) film stack formed according to implementationsdescribed herein;

FIG. 4 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure having a solid electrolyteinterphase (SEI) film stack formed according to implementationsdescribed herein;

FIG. 5 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure having a solid electrolyteinterphase (SEI) film stack formed according to implementationsdescribed herein;

FIG. 6 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure having a solid electrolyteinterphase (SEI) film stack formed according to implementationsdescribed herein;

FIG. 7 illustrates a process flow chart summarizing one implementationof a method for forming an anode electrode structure having a solidelectrolyte interphase (SEI) film stack according to implementationsdescribed herein;

FIG. 8 illustrates a process flow chart summarizing one implementationof another method for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein;

FIG. 9 illustrates a process flow chart summarizing one implementationof another method for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein;

FIG. 10 illustrates a process flow chart summarizing one implementationof another method for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein;

FIG. 11 illustrates a schematic view of an integrated processing toolfor forming anode electrode structures according to implementationsdescribed herein;

FIGS. 12A-12D are plots depicting cell voltage changes versus time for asymmetric lithium cell (1 hour cycle) at a current density of 0.25mA/cm²;

FIGS. 13A-13B are plots of impedance spectra for Li/Li symmetric cellsusing a chalcogenide modified interface according to implementationsdescribed herein;

FIG. 14 is a plot depicting a comparison of lithium control samples vs.a chalcogenide modified interface according to implementations describedherein;

FIGS. 15A-15B are SEM images of lithium for a control cell and a cellhaving a chalcogenide modified interface according to implementationsdescribed herein;

FIGS. 16A-16B are plots depicting discharge capacity versus cycle numberfor a bare lithium metal anode and a lithium metal anode protected witha chalcogenide modified interface according to implementations describedherein;

FIG. 17 is a plot depicting cell voltage versus capacity at differentdischarge rates (0.1 C to 5 C) for a lithium metal anode protected witha chalcogenide modified interface according to implementations describedherein;

FIG. 18 is a plot depicting the corresponding discharge capacityvariations vs. C rate for a lithium metal anode protected with achalcogenide modified interface according to implementations describedherein;

FIG. 19 is a plot comparing the percentage of discharge capacityretention at different discharge rates; and

FIG. 20 is a plot comparing charge rate capacity variations versus Crate for a control sample versus a lithium metal anode protected with achalcogenide modified interface according to implementations describedherein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation.

DETAILED DESCRIPTION

The following disclosure describes lithium-containing electrodes, highperformance electrochemical devices, such as secondary batteries,including the aforementioned lithium-containing electrodes, and methodsfor fabricating the same. Certain details are set forth in the followingdescription and in FIGS. 1-20 to provide a thorough understanding ofvarious implementations of the disclosure. Other details describingwell-known structures and systems often associated with electrochemicalcells and secondary batteries are not set forth in the followingdisclosure to avoid unnecessarily obscuring the description of thevarious implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Implementations described herein will be described below in reference toa roll-to-roll coating system, such as a TopMet® roll-to-roll webcoating system, a SMARTWEB® roll-to-roll web coating system, a TOPBEAM®roll-to-roll web coating system, all of which are available from AppliedMaterials, Inc. of Santa Clara, Calif. Other tools capable of performinghigh rate deposition processes may also be adapted to benefit from theimplementations described herein. In addition, any system enabling thedeposition processes described herein can be used to advantage. Theapparatus description described herein is illustrative and should not beconstrued or interpreted as limiting the scope of the implementationsdescribed herein. It should also be understood that although describedas a roll-to-roll process, the implementations described herein may alsobe performed on discrete substrates.

Development of rechargeable lithium metal batteries is considered apromising technology, which can enable a high-energy-density system forenergy storage. However, current lithium metal batteries suffer fromdendrite growth, which hinders the practical applications of lithiummetal batteries in portable electronics and electric vehicles. Over thecourse of several charge/discharge cycles, microscopic fibers oflithium, called dendrites form on the lithium metal surface and spreaduntil contacting the other electrode. Passing electrical current throughthese dendrites can short circuit the battery. One of the mostchallenging aspects of enabling lithium metal battery technology is thedevelopment of a stable and efficient solid electrolyte interphase(SEI). A stable and efficient SEI provides an effective strategy forinhibiting dendrite growth and thus achieving improved cycling.

Current SEI films are typically formed in-situ during the cell formationcycling process, which is generally performed immediately after cellfabrication. During the cell formation cycling process, when anappropriate potential is established on the anode and particular organicsolvents are used as the electrolyte, the organic solvent is decomposedand forms the SEI film at first charge. With typical liquid electrolytesand under lower current density, a mossy lithium deposit was reportedand the lithium growth was attributed to “bottom growth.” At highercurrent densities, a concentration gradient in the electrolyte causes‘tip growth’ and this tip growth causes shorting of the cell. Dependingupon the organic solvents used, the SEI film that forms on the anode istypically a mixture of lithium oxide, lithium fluoride, andsemicarbonates. Initially, the SEI film is electrically insulating yetsufficiently conductive to lithium ions. The SEI prevents decompositionof the electrolyte after the second charge. The SEI can be thought of asa three-layer system with two key interfaces. In conventionalelectrochemical studies, it is often referred to as an electrical doublelayer. In its simplest form, an anode coated by an SEI will undergothree stages when charged. These three stages include electron transferbetween the anode (M) and the SEI (M⁰-ne→M^(n+) _(M/SEI)); cationmigration from the anode-SEI interface to the SEI-electrolyte (E)interface (M^(n+) _(M/SEI)→M^(n+) _(SEI/E)); and cation transfer in theSEI to electrolyte at the SEI/electrolyte interface (E(solv)+M^(n+)_(SEI/E)→M^(n+)E(solv)).

The power density and recharge speed of the battery is dependent on howquickly the anode can release and gain charge. This, in turn, isdependent on how quickly the anode can exchange lithium ions with theelectrolyte through the SEI. Lithium ion exchange at the SEI is amulti-stage process and as with most multi-stage processes, the speed ofthe entire process is dependent upon the slowest stage. Studies haveshown that anion migration is the bottleneck for most systems. Inaddition, it is believed that the diffusive characteristics of thesolvents dictate the speed of migration between the anode-SEI interfaceand the SEI-electrolyte (E) interface. Thus, the best solvents havelittle mass in order to maximize the speed of diffusion.

Although the specific properties and reactions that take place at theSEI are not well understood, it is believed that these properties andreactions have profound effects on the cycling and capacity of the anodeelectrode structure. It is further believed that the SEI can thickenwhen cycled, slowing diffusion from the Electrode/SEI interface to theSEI/Electrolyte. For example, at elevated temperatures, alkyl carbonatesin the electrolyte decompose into insoluble Li₂CO₃ that can increase thethickness of the SEI film, clog pores of the SEI film, and limit lithiumion access to the anode. SEI growth can also occur by gas evolution atthe cathode and particle migration towards the anode. This, in turn,increases impedance and decreases capacity. Further, the randomness ofmetallic lithium embedded in the anode during intercalation results indendrite formation. Over time, the dendrites pierce the separator,causing a short circuit leading to heat, fire and/or explosion.

Implementations of the present disclosure relate to constructing astable and an efficient SEI film ex-situ. The SEI film is formed in theenergy storage device during fabrication of the energy storage device.This new and efficient SEI film is believed to inhibit lithium dendritegrowth and thus achieves superior lithium metal cycling performancerelative to current lithium based anodes, which rely on an in-situ SEIfilm.

FIG. 1 illustrates a cross-sectional view of one implementation of anenergy storage device 100 incorporating an anode electrode structurehaving an SEI film stack 140 formed according to implementationsdescribed herein. In some implementations, the energy storage device 100is a rechargeable battery cell. In some implementations, the energystorage device 100 is combined with other cells to form a rechargeablebattery. The energy storage device 100 has a cathode current collector110, a cathode film 120, a separator film 130, the SEI film stack 140,an anode film 150 and an anode current collector 160. Note in FIG. 1that the current collectors and separator are shown to extend beyond thestack, although it is not necessary for the current collectors to extendbeyond the stack, the portions extending beyond the stack may be used astabs. The SEI film stack 140 can have more than one layer, for example,a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, orBi₂Se₃ film) in combination with at least one of lithium carbonate(Li₂CO₃), lithium oxide (Li₂O), lithium nitride (Li₃N), and lithiumfluoride (LiF).

In one implementation, portions of the SEI film stack 140 are formed byexposing a lithium film to an SF₆ gas treatment to form LiF and Li₂Sportions of the SEI film stack 140 on the surface of the lithium film.The SF₆ gas can be activated to react with the exposed lithium surfaceeither thermally or SF₆ gas can be plasma activated. The thickness ofthe SEI film stack 140 can be controlled by modifying the SF₆ gasexposure time and temperature.

The current collectors 110, 160, on the cathode film 120 and the anodefilm 150, respectively, can be identical or different electronicconductors. Examples of metals that the current collectors 110, 160 maybe comprised of include aluminum (Al), copper (Cu), zinc (Zn), nickel(Ni), cobalt (Co), tin (Sn), silicon (Si), manganese (Mn), magnesium(Mg), alloys thereof, and combinations thereof. In one implementation,at least one of the current collectors 110, 160 is perforated.Furthermore, current collectors may be of any form factor (e.g.,metallic foil, sheet, or plate), shape and micro/macro structure. In oneimplementation, at least one of the current collectors 110, 160 includea polyethylene terephthalate (“PET”) film coated with a metallicmaterial. In one implementation, the anode current collector 160 is aPET film coated with copper. In another implementation, the anodecurrent collector 160 is a multi-metal layer on PET. The multi-metallayer can be combinations of copper, chromium, nickel, etc. In oneimplementation, the anode current collector 160 is a multi-layerstructure that includes a copper-nickel cladding material. In oneimplementation, the multi-layer structure includes a first layer ofnickel or chromium, a second layer of copper formed on the first layer,and a third layer including nickel, chromium, or both formed on thesecond layer. In one implementation, the anode current collector 160 isnickel coated copper. Furthermore, current collectors may be of any formfactor (e.g., metallic foil, sheet, or plate), shape and micro/macrostructure. Generally, in prismatic cells, tabs are formed of the samematerial as the current collector and may be formed during fabricationof the stack, or added later. All components except current collectors110 and 160 contain lithium ion electrolytes. In one implementation, thecathode current collector 110 is aluminum. In one implementation, thecathode current collector 110 has a thickness from about 0.5 μm to about20 μm (e.g., from about 1 μm to about 10 μm; from about 5 μm to about 10μm). In one implementation, the anode current collector 160 is copper.In one implementation, the anode current collector 160 has a thicknessfrom about 0.5 μm to about 20 μm (e.g., from about 1 μm to about 10 μm;from about 2 μm to about 8 μm; from about 5 μm to about 10 μm).

The anode film 150 or anode may be any material compatible with thecathode film 120 or cathode. The anode film 150 may have an energycapacity greater than or equal to 372 mAh/g, preferably 700 mAh/g, andmost preferably 1000 mAh/g. The anode film 150 may be constructed fromlithium metal, lithium metal foil or a lithium alloy foil (e.g. lithiumaluminum alloys), or a mixture of a lithium metal and/or lithium alloyand materials such as carbon (e.g. coke, graphite), nickel, copper, tin,indium, silicon, oxides thereof, or combinations thereof. The anode film150 typically comprises intercalation compounds containing lithium orinsertion compounds containing lithium. In some implementations, whereinthe anode film 150 comprises lithium metal, the lithium metal may bedeposited using the methods described herein. The anode film may beformed by extrusion, physical or chemical thin-film techniques, such assputtering, electron beam evaporation, chemical vapor deposition (CVD),three-dimensional printing, lithium powder deposition etc. In oneimplementation, the anode film 150 has a thickness from about 0.5 μm toabout 20 μm (e.g., from about 1 μm to about 10 μm; from about 5 μm toabout 10 μm). In one implementation, the anode film 150 is a lithiummetal or lithium metal alloy film.

The SEI film stack 140 is formed ex-situ on the anode film 150. The SEIfilm stack 140 is electrically insulating yet sufficiently conductive tolithium-ions. In one implementation, the SEI film stack 140 is anonporous film. In another implementation, the SEI film stack 140 is aporous film. In one implementation, the SEI film stack 140 has aplurality of nanopores that are sized to have an average pore size ordiameter less than about 10 nanometers (e.g., from about 1 nanometer toabout 10 nanometers; from about 3 nanometers to about 5 nanometers). Inanother implementation, the SEI film stack 140 has a plurality ofnanopores that are sized to have an average pore size or diameter lessthan about 5 nanometers. In one implementation, the SEI film stack 140has a plurality of nanopores having a diameter ranging from about 1nanometer to about 20 nanometers (e.g., from about 2 nanometers to about15 nanometers; or from about 5 nanometers to about 10 nanometers).

The SEI film stack 140 may be a coating or a discrete layer, eitherhaving a thickness in the range of 1 nanometer to 200 nanometers (e.g.,in the range of 5 nanometers to 200 nanometers; in the range of 10nanometers to 50 nanometers). Not to be bound by theory, but it isbelieved that SEI films greater than 200 nanometers may increaseresistance within the rechargeable battery.

Examples of materials that may be included in the SEI film stack 140include, but are not limited to a chalcogenide film (e.g., CuS, Cu₂Se,Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) or composite chalcogenidefilm optionally in combination with at least one of a lithium carbonate(Li₂CO₃) film, a lithium oxide (Li₂O) film, a lithium nitride film(Li₃N), and a lithium halide film (e.g. LiF, LiCl, LiBr, or Lil). In oneimplementation, the SEI film stack 140 is a chalcogenide film (e.g.,CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film). Not to be boundby theory but it is believed that the SEI film stack 140 can take-upLi-conducting electrolyte to form gel during device fabrication which isbeneficial for forming good solid electrolyte interface (SEI) and alsohelps lower resistance. Suitable methods for depositing portions of theSEI film stack 140 directly on the lithium metal film include, but arenot limited to, Physical Vapor Deposition (PVD), such as evaporation orsputtering, a slot-die process, a thin-film transfer process, or athree-dimensional lithium printing process. Portions of the SEI filmstack may be formed by plasma treatment of previously deposited layers(e.g., oxygen plasma treatment of an exposed lithium surface to form alithium oxide film).

The cathode film 120 or cathode may be any material compatible with theanode and may include an intercalation compound, an insertion compound,or an electrochemically active polymer. Suitable intercalation materialsinclude, for example, lithium-containing metal oxides, MoS₂, FeS₂, MnO₂,TiS₂, NbSe₃, LiCoO₂, LiNiO₂, LiMnO₂, LiMn₂O₄, V₆O₁₃, and V₂O₅. Suitablepolymers include, for example, polyacetylene, polypyrrole, polyaniline,and polythiophene. The cathode film 120 or cathode may be made from alayered oxide, such as lithium cobalt oxide, an olivine, such as lithiumiron phosphate, or a spinel, such as lithium manganese oxide. Exemplarylithium-containing oxides may be layered, such as lithium cobalt oxide(LiCoO₂), or mixed metal oxides, such as LiNi_(x)Co_(1-2x)MnO₂,LiNiMnCoO₂ (“NMC”), LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, and doped lithium richlayered-layered materials, wherein x is zero or a non-zero number.Exemplary phosphates may be iron olivine (LiFePO₄) and it is variants(such as LiFe_((1-x))Mg_(x)PO₄, wherein x is between 0 and 1), LiMoPO₄,LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄, LiMP₂O₇, or LiFe_(1.5)P₂O₇,wherein x is zero or a non-zero number. Exemplary fluorophosphates maybe LiVPO₄F, LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, orLi₂NiPO₄F. Exemplary silicates may be Li₂FeSiO₄, Li₂MnSiO₄, orLi₂VOSiO₄. An exemplary non-lithium compound is Na₅V₂(PO₄)₂F₃. Thecathode film 120 may be formed by physical or chemical thin-filmtechniques, such as sputtering, electron beam evaporation, chemicalvapor deposition (CVD), etc. In one implementation, the cathode film 120has a thickness from about 10 μm to about 100 μm (e.g., from about 30 μmto about 80 μm; or from about 40 μm to about 60 μm). In oneimplementation, the cathode film 120 is a LiCoO₂ film. In anotherimplementation, the cathode film 120 is an NMC film.

The separator film 130 comprises a porous (e.g., microporous) polymericsubstrate capable of conducting ions (e.g., a separator film) withpores. In some implementations, the porous polymeric substrate itselfdoes not need to be ion conducting, however, once filled withelectrolyte (liquid, gel, solid, combination etc.), the combination ofporous substrate and electrolyte is ion conducting. In oneimplementation, the porous polymeric substrate is a multi-layerpolymeric substrate. In one implementation, the pores are micropores. Insome implementations, the porous polymeric substrate consists of anycommercially available polymeric microporous membranes (e.g., single-plyor multi-ply), for example, those products produced by Polypore (CelgardInc., of Charlotte, N.C.), Toray Tonen (Battery separator film (BSF)),SK Energy (Li-ion battery separator (LiBS), Evonik industries (SEPARION®ceramic separator membrane), Asahi Kasei (Hipore™ polyolefin flat filmmembrane), DuPont (Energain®), etc. In some implementations, the porouspolymeric substrate has a porosity in the range of 20 to 80% (e.g., inthe range of 28 to 60%). In some implementations, the porous polymericsubstrate has an average pore size in the range of 0.02 to 5 microns(e.g., 0.08 to 2 microns). In some implementations, the porous polymericsubstrate has a Gurley Number in the range of 15 to 150 seconds (GurleyNumber refers to the time it takes for 10 cc of air at 12.2 inches ofwater to pass through one square inch of membrane). In someimplementations, the porous polymeric substrate is polyolefinic.Exemplary polyolefins include polypropylene, polyethylene, orcombinations thereof.

In some implementations of the energy storage device of the presentdisclosure, lithium is contained in the lithium metal film of the anodeelectrode, and lithium manganese oxide (LiMnO₄) or lithium cobalt oxide(LiCoO₂) at the cathode electrode, for example, although in someimplementations, the anode electrode may also include lithium absorbingmaterials such as silicon, tin, etc. The energy storage device, eventhough shown as a planar structure, may also be formed into a cylinderby rolling the stack of layers; furthermore, implementations of thepresent disclosure also contemplate other cell configurations (e.g.,prismatic cells, button cells).

Electrolytes infused in cell components 120, 130, 140 and 150 can becomprised of a liquid/gel or a solid polymer and may be different ineach. In some implementations, the electrolyte primarily includes a saltand a medium (e.g., in a liquid electrolyte, the medium may be referredto as a solvent; in a gel electrolyte, the medium may be a polymermatrix). The salt may be a lithium salt. The lithium salt may include,for example, LiPF₆, LiAsF₆, LiCF₃SO₃, LiN(CF₃SO₃)₃, LiBF₆, and LiClO₄,lithium bistrifluoromethanesulfonimidate (e.g., LiTFSI), BETTEelectrolyte (commercially available from 3M Corp. of Minneapolis, Minn.)and combinations thereof. Solvents may include, for example, ethylenecarbonate (EC), propylene carbonate (PC), EC/PC,2-MeTHF(2-methyltetrahydrofuran)/EC/PC, EC/DMC (dimethyl carbonate),EC/DME (dimethyl ethane), EC/DEC (diethyl carbonate), EC/EMC (ethylmethyl carbonate), EC/EMC/DMC/DEC, EC/EMC/DMC/DEC/PE, PC/DME, andDME/PC. Polymer matrices may include, for example, PVDF (polyvinylidenefluoride), PVDF:THF (PVDF:tetrahydrofuran), PVDF:CTFE (PVDF:chlorotrifluoroethylene) PAN (polyacrylonitrile), and PEO (polyethyleneoxide).

FIG. 2 illustrates a cross-sectional view of one implementation of adual-sided anode electrode structure 200 having a solid electrolyteinterphase (SEI) film stack 240 a, 240 b (collectively 240) formedaccording to implementations described herein. The SEI film stack 240 a,240 b may be used in place of the SEI film stack 140 depicted in FIG. 1.Each SEI film stack 240 a, 240 b includes a chalcogenide film 210 a, 210b (collectively 210) respectively formed on each anode film 150 a, 150b. The chalcogenide film is selected from the group of copperchalcogenide (e.g., CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe), bismuth chalcogenide(e.g., Bi₂Te₃, Bi₂Se₃), and combinations thereof.

FIG. 3 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure 300 having a solid electrolyteinterphase (SEI) film stack 340 a, 340 b (collectively 340) formedaccording to implementations described herein. The SEI film stack 340 a,340 b may be used in place of the SEI film stack 140 depicted in FIG. 1.Each SEI film stack 340 a, 340 b includes the chalcogenide film 210 a,210 b respectively formed on each anode film 150 a, 150 b. Thechalcogenide film is selected from the group of copper chalcogenide(e.g., CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe), bismuth chalcogenide (e.g.,Bi₂Te₃, Bi₂Se₃), and combinations thereof. Each SEI film stack 340 a,340 b further includes a Li₂O film 310 a, 310 b (collectively 310)formed on the chalcogenide film 210 a, 210 b. Each SEI film stack 340 a,340 b further includes a Li₂CO₃ film 320 a, 320 b (collectively 320)formed on the Li₂O film 310 a, 310 b (collectively 310).

FIG. 4 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure 400 having a solid electrolyteinterphase (SEI) film stack 440 a, 440 b (collectively 440) formedaccording to implementations described herein. The SEI film stack 440 a,440 b may be used in place of the SEI film stack 140 depicted in FIG. 1.Each SEI film stack 440 a, 440 b includes a Li₂O film 310 a, 310 b(collectively 310) respectively formed on each anode film 150 a, 150 b.Each SEI film stack 440 a, 440 b further includes a Li₂CO₃ film 320 a,320 b formed on the Li₂O film 310 a, 310 b. Each SEI film stack 440 a,440 b further includes the chalcogenide film 210 a, 210 b formed on theLi₂CO₃ film 320 a, 320 b.

FIG. 5 illustrates a cross-sectional view of another implementation of adual-sided anode electrode structure 500 having a solid electrolyteinterphase (SEI) film stack 540 a, 540 b (collectively 540) formedaccording to implementations described herein. The SEI film stack 540 a,540 b may be used in place of the SEI film stack 140 depicted in FIG. 1.Each SEI film stack 540 a, 540 b includes a lithium nitride (Li₃N) film510 a, 510 b (collectively 510) respectively formed on each anode film150 a, 150 b. Each SEI film stack 540 a, 540 b further includes a Li₂Ofilm 310 a, 310 b respectively formed on each lithium nitride film 510a, 510 b. Each SEI film stack 540 a, 540 b further includes a Li₂CO₃film 320 a, 320 b formed on the Li₂O film 310 a, 310 b. Each SEI filmstack 540 a, 540 b further includes the chalcogenide film 210 a, 210 bformed on the Li₂CO₃ film 320 a, 320 b.

FIG. 6 illustrates a cross-sectional view of one implementation of adual-sided anode electrode structure 600 having a solid electrolyteinterphase (SEI) film stack 640 a, 640 b (collectively 640) formedaccording to implementations described herein. The SEI film stack 640 a,640 b may be used in place of the SEI film stack 140 depicted in FIG. 1.Each SEI film stack 640 a, 640 b includes the chalcogenide film 210 a,210 b respectively formed on each anode film 150 a, 150 b. Thechalcogenide film is selected from the group of copper chalcogenide(e.g., CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe), bismuth chalcogenide (e.g.,Bi₂Te₃, Bi₂Se₃), and combinations thereof. Each SEI film stack 640 a,640 b further includes a lithium halide film 610 a, 610 b (collectively610) formed on the chalcogenide film 210 a, 210 b. In oneimplementation, the lithium halide film is selected form LiF, LiCl,LiBr, and Lil.

Note in FIGS. 2-6 that the anode current collector 160 is shown toextend beyond the stack, although it is not necessary for the anodecurrent collector 160 to extend beyond the stack, the portions extendingbeyond the stack may be used as tabs. Although the anode electrodestructures depicted in FIGS. 2-6 are depicted as dual-sided electrodestructures, it should be understood that the implementations describedin FIGS. 2-6 also apply to single-sided electrode structures.

FIG. 7 illustrates a process flow chart summarizing one implementationof a method 700 for forming an anode electrode structure having a solidelectrolyte interphase (SEI) film stack according to implementationsdescribed herein. In one implementation, the anode electrode structureis the dual-sided anode electrode structure 200 depicted in FIG. 2. Inanother implementation, the anode electrode structure is the dual-sidedanode electrode structure 300 depicted in FIG. 3. At operation 710, asubstrate is provided. In one implementation, the substrate is acontinuous sheet of material 1150 as shown in FIG. 11. In oneimplementation, the substrate is the anode current collector 160.Examples of metals that the substrate may be comprised of includealuminum (Al), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co),manganese (Mn), chromium (Cr), stainless steel, clad materials, alloysthereof, and combinations thereof. In one implementation, the substrateis copper material. In one implementation, the substrate is perforated.Furthermore, the substrate may be of any form factor (e.g., metallicfoil, sheet, or plate), shape and micro/macro structure.

In some implementations, the substrate is exposed to a pretreatmentprocess, which includes at least one of a plasma treatment or coronadischarge process to remove organic materials from the exposed surfacesof the current collector. The pretreatment process is performed prior tofilm deposition on the substrate.

At operation 720, a lithium metal film is formed on the substrate. Inone implementation, the lithium metal film is the anode film 150 and thesubstrate is the anode current collector 160. In one implementation, thelithium metal film is formed on a copper current collector. In someimplementations, if an anode film is already present on the substrate,the lithium metal film is formed on the anode film. If the anode film150 is not present, the lithium metal film may be formed directly on thesubstrate. Any suitable lithium metal film deposition process fordepositing thin films of lithium metal may be used to deposit the thinfilm of lithium metal. Deposition of the thin film of lithium metal maybe by PVD processes, such as evaporation, a sputtering process, aslot-die process, a transfer process, or a three-dimensional lithiumprinting process. The chamber for depositing the thin film of lithiummetal may include a PVD system, such as an electron-beam evaporator, athermal evaporator, or a sputtering system, a thin film transfer system(including large area pattern printing systems such as gravure printingsystems) or a slot-die deposition system. In one implementation, theanode film 150 has a thickness of 100 micrometers or less (e.g., fromabout 1 μm to about 100 μm; from about 3 μm to about 30 μm; from about20 μm to about 30 μm; from about 1 μm to about 20 μm; or from about 50μm to about 100 μm).

At operation 730, an SEI film stack is formed on the lithium metal film.The SEI film stack includes a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S,Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) and optionally a lithium carbonate(Li₂CO₃) film and lithium oxide (Li₂O) film. In one implementation, theSEI film stack includes a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S,Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) only, similar to the SEI film stack240 depicted in FIG. 2. In another implementation, the SEI film stackincludes a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe,Bi₂Te₃, or Bi₂Se₃ film), a lithium oxide film formed on the chalcogenidefilm, and a lithium carbonate film formed on the lithium oxide filmonly, similar to the SEI film stack 340 depicted in FIG. 3.

At operation 740, a chalcogenide film is formed on the lithium metalfilm. In one implementation, the chalcogenide film is a Bi₂Te₃ film. Inone implementation, the chalcogenide film is the chalcogenide film 210depicted in FIGS. 2-6. In one implementation, the chalcogenide film hasa thickness of 500 nanometers or less (e.g., from about 1 nm to about400 nm; from about 25 nm to about 300 nm; from about 50 nm to about 200nm; from about 100 nm to about 150 nm; from about 10 nm to about 80 nm;or from about 30 to about 60 nanometers). In one implementation, thechalcogenide film is deposited using a PVD process having an RF powersource coupled to a target. The target is typically composed of thematerials of the chalcogenide film. In one implementation, the target isa bismuth-telluride alloy target. In one implementation, thebismuth-telluride alloy target comprises from about 5 at. % to about 95at. % bismuth and from about 5 at. % to about 95 at. % tellurium. Theplasma may be generated from a non-reactive gas such as argon (Ar),krypton (Kr), nitrogen, etc. For example, a plasma may be generated fromargon gas having a flow rate within a range from about 30 standard cubiccentimeters (sccm) to about 200 sccm, such as about 100 sccm to about150 sccm. An RF power may be applied to the target at a power levelwithin a range from about 50 W to about 4,000 W, for example, about 1000W to about 3000 W, such as about 2000 W. The deposition chamber may bepressurized from about 0.1 mTorr to about 500 mTorr. The depositionchamber may be pressurized from about 0.1 mTorr to about 100 mTorr, forexample, from about 10 mTorr to about 30 mTorr, such as 25 mTorr. Thesubstrate may be electrically “floating” and have no bias. Thedeposition process of operation 740 may be performed at a depositiontemperature from about 50° C. to about 400° C., for example, from about100° C. to about 200° C., such as about 120° C.

In another implementation, the plasma may be generated using a DC powersource coupled to bismuth-telluride alloy target. The substrate may beelectrically “floating” and have no bias. In this implementation, plasmamay be generated from an argon gas having a flow rate within a rangefrom about 30 standard cubic centimeters (sccm) to about 200 sccm, suchas about 100 sccm to about 150 sccm. A DC power may be applied to thetarget at a power level within a range from about 50 W to about 5,000 W,from about 1000 W to about 3000 W, for example between about 1000 W toabout 2000 W, such as about 2000 W. The deposition chamber may bepressurized from about 0.1 mTorr to about 500 mTorr. The depositionchamber may be pressurized from about 0.1 mTorr to about 100 mTorr, forexample, from about 10 mTorr to about 30 mTorr, such as 25 mTorr. Thesubstrate may be electrically “floating” and have no bias. Thedeposition process of operation 740 may be performed at a depositiontemperature from about 50° C. to about 400° C., for example, from about100° C. to about 200° C., such as about 120° C.

Optionally, at operation 750, a lithium oxide (Li₂O) film is formed onthe chalcogenide film. In one implementation, the lithium oxide film isthe lithium oxide film 310 depicted in FIGS. 2-6. In one implementation,the lithium oxide film has a thickness of 500 nanometers or less (e.g.,from about 1 nm to about 4000 nm; from about 25 nm to about 300 nm; fromabout 50 nm to about 200 nm; or from about 100 nm to about 150 nm). Inone implementation, the lithium oxide film is formed by depositing anadditional lithium metal film on the chalcogenide film and exposing thelithium metal film to a plasma oxidation process to oxidize the lithiummetal film. In one implementation, the lithium oxide film is formed bydepositing an additional lithium metal film via PVD in anoxygen-containing atmosphere. In one implementation, portions of thelithium metal film deposited during operation 720 remain exposed afterdeposition of the chalcogenide film during operation 740. The exposedportions of lithium metal film are then exposed to a plasma oxidationprocess to form the lithium oxide film.

Optionally, at operation 760, a lithium carbonate (Li₂CO₃) film isformed on the lithium oxide film. In one implementation, the lithiumcarbonate film is the lithium carbonate film 320 depicted in FIGS. 3-5.In one implementation, the lithium carbonate film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; or from about 100nm to about 150 nm). In one implementation, the lithium carbonate filmis formed by depositing an additional lithium metal film on the lithiumoxide film and exposing the lithium metal film to a plasma oxidationprocess (e.g., gas treatment using at least one of O₂ and CO₂) tooxidize the lithium metal film. In one implementation, the lithium oxidefilm is formed by depositing an additional lithium metal film via PVD inan oxygen-containing atmosphere (e.g., atmosphere containing at leastone of O₂ and CO₂). In one implementation, portions of the lithium oxidefilm deposited during operation 750 are exposed to a plasma oxidationprocess to form the lithium carbonate film.

FIG. 8 illustrates a process flow chart summarizing one implementationof another method 800 for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein. In one implementation, the anodeelectrode structure is the dual-sided anode electrode structure 400depicted in FIG. 4. In another implementation, the anode electrodestructure is the dual-sided anode electrode structure 500 depicted inFIG. 5. At operation 810, a substrate is provided. In oneimplementation, the substrate is the continuous sheet of material 1150as shown in FIG. 11. In one implementation, the substrate is the anodecurrent collector 160. Examples of metals that the substrate may becomprised of include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni),cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, cladmaterials, alloys thereof, and combinations thereof. In oneimplementation, the substrate is copper material. In one implementation,the substrate is perforated. Furthermore, the substrate may be of anyform factor (e.g., metallic foil, sheet, or plate), shape andmicro/macro structure.

In some implementations, the substrate is exposed to a pretreatmentprocess, which includes at least one of a plasma treatment or coronadischarge process to remove organic materials from the exposed surfacesof the current collector. The pretreatment process is performed prior tofilm deposition on the substrate.

At operation 820, a lithium metal film is formed on the substrate. Inone implementation, the lithium metal film is the anode film 150 and thesubstrate is the anode current collector 160. In one implementation, thelithium metal film is formed on a copper current collector. In someimplementations, if an anode film is already present on the substrate,the lithium metal film is formed on the anode film. If the anode film150 is not present, the lithium metal film may be formed directly on thesubstrate. Any suitable lithium metal film deposition process fordepositing thin films of lithium metal may be used to deposit the thinfilm of lithium metal. Deposition of the thin film of lithium metal maybe by PVD processes, such as evaporation, a sputtering process, aslot-die process, a transfer process, or a three-dimensional lithiumprinting process. The chamber for depositing the thin film of lithiummetal may include a PVD system, such as an electron-beam evaporator, athermal evaporator, or a sputtering system, a thin film transfer system(including large area pattern printing systems such as gravure printingsystems) or a slot-die deposition system. In one implementation, theanode film 150 has a thickness of 100 micrometers or less (e.g., fromabout 1 μm to about 100 μm; from about 3 μm to about 30 μm; from about20 μm to about 30 μm; from about 1 μm to about 20 μm; or from about 50μm to about 100 μm).

At operation 830, an SEI film stack is formed on the lithium metal film.The SEI film stack includes a lithium oxide (Li₂O) film, a lithiumcarbonate (Li₂CO₃) film, a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S,Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) and optionally a lithium nitride(Li₃N) film (See FIG. 5). In one implementation, the SEI film stackincludes a lithium nitride (Li₃N) film formed on the lithium metal film,a lithium oxide (Li₂O) film formed on the lithium nitride film, alithium carbonate (Li₂CO₃) film formed on the lithium oxide film, and achalcogenide film (e.g., Bi₂Te₃ film) formed on the lithium carbonatefilm, similar to the SEI film stack 540 depicted in FIG. 5. In anotherimplementation, the SEI film stack includes a lithium oxide (Li₂O) filmformed on the lithium metal film, a lithium carbonate (Li₂CO₃) filmformed on the lithium oxide film, and a chalcogenide film (e.g., CuS,Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) formed on the lithiumcarbonate film, similar to the SEI film stack 440 depicted in FIG. 4.

Optionally, at operation 840, a lithium nitride (Li₃N) film is formed onthe lithium metal film. In one implementation, the lithium nitride filmis the lithium nitride film 510 depicted in FIG. 5. In oneimplementation, the lithium nitride film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; or from about 1 nmto about 50 nm). In one implementation, the lithium nitride film isformed by depositing an additional lithium metal film on the lithiummetal film and exposing the lithium metal film to a plasma nitridationprocess to form the lithium nitride film. In one implementation, thelithium nitride film is formed by depositing an additional lithium metalfilm via PVD in a nitrogen-containing atmosphere.

At operation 850, a lithium oxide (Li₂O) film is formed. If the lithiumnitride film is present, the lithium oxide film is formed on the lithiumnitride film. If the lithium nitride is not present, the lithium oxidefilm is formed on the lithium metal film. In one implementation, thelithium oxide film is the lithium oxide film 310 depicted in FIGS. 4-5.In one implementation, the lithium oxide film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 4000 nm; from about25 nm to about 300 nm; from about 50 nm to about 200 nm; or from about100 nm to about 150 nm). In one implementation, the lithium oxide filmis formed by depositing an additional lithium metal film on the lithiumnitride film and exposing the lithium metal film to a plasma oxidationprocess to oxidize the lithium metal film. In one implementation, thelithium oxide film is formed by depositing an additional lithium metalfilm via PVD in an oxygen-containing atmosphere. In one implementation,the lithium nitride film is exposed to a plasma oxidation process toform the lithium oxide film. In one implementation where the lithiumnitride film is not present, the lithium metal film deposited duringoperation 820 is exposed to a plasma oxidation process to form thelithium oxide film.

At operation 860, a lithium carbonate (Li₂CO₃) film is formed on thelithium oxide film. In one implementation, the lithium carbonate film isthe lithium carbonate film 320 depicted in FIGS. 4-5. In oneimplementation, the lithium carbonate film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; or from about 100nm to about 150 nm). In one implementation, the lithium carbonate filmis formed by depositing an additional lithium metal film on the lithiumoxide film and exposing the lithium metal film to a plasma oxidationprocess (e.g., gas treatment using at least one of O₂ and CO₂) tooxidize the lithium metal film. In one implementation, the lithium oxidefilm is formed by depositing an additional lithium metal film via PVD inan oxygen-containing atmosphere (e.g., atmosphere containing at leastone of O₂ and CO₂). In one implementation, portions of the lithium oxidefilm deposited during operation 750 are exposed to a plasma oxidationprocess to form the lithium carbonate film.

At operation 870, a chalcogenide film is formed on the lithium carbonatefilm. In one implementation, the chalcogenide film is a Bi₂Te₃ film. Inone implementation, the chalcogenide film is the chalcogenide film 210depicted in FIGS. 4-5. In one implementation, the chalcogenide film isdeposited using the process conditions described in operation 740. Inone implementation, the chalcogenide film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; from about 100 nmto about 150 nm; from about 10 nm to about 80 nm; or from about 30 toabout 60 nanometers). The chalcogenide film may be formed using anysuitable deposition process. In one implementation, the chalcogenidefilm is deposited using the processes described for operation 740.

FIG. 9 illustrates a process flow chart summarizing one implementationof another method 900 for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein. In one implementation, the anodeelectrode structure is the dual-sided anode electrode structure 600depicted in FIG. 6. At operation 910, a substrate is provided. In oneimplementation, the substrate is the continuous sheet of material 1150as shown in FIG. 11. In one implementation, the substrate is the anodecurrent collector 160. Examples of metals that the substrate may becomprised of include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni),cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, cladmaterials, alloys thereof, and combinations thereof. In oneimplementation, the substrate is copper material. In one implementation,the substrate is perforated. Furthermore, the substrate may be of anyform factor (e.g., metallic foil, sheet, or plate), shape andmicro/macro structure.

In some implementations, the substrate is exposed to a pretreatmentprocess, which includes at least one of a plasma treatment or coronadischarge process to remove organic materials from the exposed surfacesof the current collector. The pretreatment process is performed prior tofilm deposition on the substrate.

At operation 920, a lithium metal film is formed on the substrate. Inone implementation, the lithium metal film is the anode film 150 and thesubstrate is the anode current collector 160. In one implementation, thelithium metal film is formed on a copper current collector. In someimplementations, if an anode film is already present on the substrate,the lithium metal film is formed on the anode film. If the anode film150 is not present, the lithium metal film may be formed directly on thesubstrate. Any suitable lithium metal film deposition process fordepositing thin films of lithium metal may be used to deposit the thinfilm of lithium metal. Deposition of the thin film of lithium metal maybe by PVD processes, such as evaporation, a sputtering process, aslot-die process, a transfer process, or a three-dimensional lithiumprinting process. The chamber for depositing the thin film of lithiummetal may include a PVD system, such as an electron-beam evaporator, athermal evaporator, or a sputtering system, a thin film transfer system(including large area pattern printing systems such as gravure printingsystems) or a slot-die deposition system. In one implementation, theanode film 150 has a thickness of 100 micrometers or less (e.g., fromabout 1 μm to about 100 μm; from about 3 μm to about 30 μm; from about20 μm to about 30 μm; from about 1 μm to about 20 μm; or from about 50μm to about 100 μm).

At operation 930, an SEI film stack is formed on the lithium metal film.The SEI film stack includes a chalcogenide film (e.g., CuS, Cu₂Se, Cu₂S,Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) and a lithium fluoride (LiF) filmformed on the chalcogenide film similar to the SEI film stack 640depicted in FIG. 6.

At operation 940, a chalcogenide film is formed on the lithium carbonatefilm. In one implementation, the chalcogenide film is a Bi₂Te₃ film. Inone implementation, the chalcogenide film is the chalcogenide film 210depicted in FIGS. 4-5. In one implementation, the chalcogenide film isdeposited using the process conditions described in operation 740. Inone implementation, the chalcogenide film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; from about 100 nmto about 150 nm; from about 10 nm to about 80 nm; or from about 30 toabout 60 nanometers). The chalcogenide film may be formed using anysuitable deposition process. In one implementation, the chalcogenidefilm is deposited using the processes described for operation 740.

At operation 950, a lithium halide film is formed on the chalcogenidefilm. In one implementation, the lithium halide film is the lithiumhalide film 610 depicted in FIG. 6. In one implementation, the lithiumhalide film is deposited on the chalcogenide film by Physical VaporDeposition (PVD), such as evaporation or sputtering, special atomiclayer deposition (ALD), a slot-die process, a thin-film transferprocess, or a three-dimensional lithium printing process. In oneimplementation, PVD is the method for deposition of the lithium fluoridefilm. In one implementation, the lithium halide film is selected formLiF, LiCl, LiBr, and Lil. In one implementation, the lithium halide filmis a lithium fluoride film. In one implementation, the lithium halidefilm is deposited using a thermal evaporation process. In oneimplementation, the lithium fluoride film has a thickness of 500nanometers or less (e.g., from about 1 nm to about 400 nm; from about 25nm to about 300 nm; from about 50 nm to about 200 nm; or from about 100nm to about 150 nm).

FIG. 10 illustrates a process flow chart summarizing one implementationof another method 1000 for forming an anode electrode structure having asolid electrolyte interphase (SEI) film stack according toimplementations described herein. In one implementation, the anodeelectrode structure is the dual-sided anode electrode structure 600depicted in FIG. 6. At operation 1010, a substrate is provided. In oneimplementation, the substrate is the continuous sheet of material 1150as shown in FIG. 11. In one implementation, the substrate is the anodecurrent collector 160. Examples of metals that the substrate may becomprised of include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni),cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, cladmaterials, alloys thereof, and combinations thereof. In oneimplementation, the substrate is copper material. In one implementation,the substrate is perforated. Furthermore, the substrate may be of anyform factor (e.g., metallic foil, sheet, or plate), shape andmicro/macro structure.

In some implementations, the substrate is exposed to a pretreatmentprocess, which includes at least one of a plasma treatment or coronadischarge process to remove organic materials from the exposed surfacesof the current collector. The pretreatment process is performed prior tofilm deposition on the substrate.

At operation 1020, a lithium metal film is formed on the substrate. Inone implementation, the lithium metal film is the anode film 150 and thesubstrate is the anode current collector 160. In one implementation, thelithium metal film is formed on a copper current collector. In someimplementations, if an anode film is already present on the substrate,the lithium metal film is formed on the anode film. If the anode film150 is not present, the lithium metal film may be formed directly on thesubstrate. Any suitable lithium metal film deposition process fordepositing thin films of lithium metal may be used to deposit the thinfilm of lithium metal. Deposition of the thin film of lithium metal maybe by PVD processes, such as evaporation, a sputtering process, aslot-die process, a transfer process, or a three-dimensional lithiumprinting process. The chamber for depositing the thin film of lithiummetal may include a PVD system, such as an electron-beam evaporator, athermal evaporator, or a sputtering system, a thin film transfer system(including large area pattern printing systems such as gravure printingsystems) or a slot-die deposition system. In one implementation, theanode film 150 has a thickness of 100 micrometers or less (e.g., fromabout 1 μm to about 100 μm; from about 3 μm to about 30 μm; from about20 μm to about 30 μm; from about 1 μm to about 20 μm; or from about 50μm to about 100 μm).

At operation 1030, an SEI film stack is formed on the lithium metalfilm. The SEI film stack includes a lithium halide and chalcogenidecomposite film. In one implementation, the SEI film stack furthercomprises at least one of a lithium fluoride (LiF) film, a lithiumcarbonate (Li₂CO₃) film, a lithium oxide film, a lithium nitride (Li₃N)film, a chalcogenide film and combinations thereof. The composite filmmay be a composite film comprising chalcogenide materials (e.g., CuS,Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, or Bi₂Se₃ film) and lithium halidematerials (e.g., lithium fluoride).

At operation 1040, the lithium halide and the chalcogenide compositefilm is formed on the underlying film (e.g., lithium metal film). In oneimplementation, the lithium halide and the chalcogenide composite filmis a LiF and Bi₂Te₃ composite film. In one implementation, the lithiumhalide and chalcogenide composite film is the chalcogenide film 210depicted in FIGS. 4-5. In one implementation, the lithium halide andchalcogenide composite film is deposited using the process conditionsdescribed in operation 740, operation 940, or a combination of theprocesses of operation 740 and 940. In one implementation, the lithiumhalide and chalcogenide composite film has a thickness of 500 nanometersor less (e.g., from about 1 nm to about 400 nm; from about 25 nm toabout 300 nm; from about 50 nm to about 200 nm; from about 100 nm toabout 150 nm; from about 10 nm to about 80 nm; or from about 30 to about60 nanometers). The lithium halide and chalcogenide composite film maybe formed using any suitable deposition process. In one implementation,the lithium halide and chalcogenide composite film is deposited byPhysical Vapor Deposition (PVD), such as evaporation or sputtering,special atomic layer deposition (ALD), a slot-die process, a thin-filmtransfer process, three-dimensional lithium printing process, orcombinations thereof. In one implementation, PVD is the method fordeposition of the lithium fluoride film.

FIG. 11 illustrates a schematic view of a flexible substrate coatingapparatus 1100 for forming anode electrode structures according toimplementations described herein. The flexible substrate coatingapparatus 1100 may be a SMARTWEB®, manufactured by Applied Materials,adapted for manufacturing lithium anode devices according to theimplementations described herein. According to typical implementations,the flexible substrate coating apparatus 1100 can be used formanufacturing lithium anodes, and particularly for SEI film stacks forlithium anodes. The flexible substrate coating apparatus 1100 isconstituted as a roll-to-roll system including an unwinding module 1102,a processing module 1104 and a winding module 1106. In certainimplementations, the processing module 1104 comprises a plurality ofprocessing modules or chambers 1110, 1120, 1130 and 1140 arranged insequence, each configured to perform one processing operation to thecontinuous sheet of material 1150 or web of material. In oneimplementation, as depicted in FIG. 11, the processing chambers1110-1140 are radially disposed about a coating drum 1155. Arrangementsother than radial are contemplated. For example, in anotherimplementation, the processing chambers may be positioned in a linearconfiguration.

In one implementation, the processing chambers 1110-1140 are stand-alonemodular processing chambers wherein each modular processing chamber isstructurally separated from the other modular processing chambers.Therefore, each of the stand-alone modular processing chambers, can bearranged, rearranged, replaced, or maintained independently withoutaffecting each other. Although four processing chambers 1110-1140 areshown, it should be understood that any number of processing chambersmay be included in the flexible substrate coating apparatus 1100.

The processing chambers 1110-1140 may include any suitable structure,configuration, arrangement, and/or components that enable the flexiblesubstrate coating apparatus 1100 to deposit a lithium anode deviceaccording to implementations of the present disclosure. For example, butnot limited to, the processing chambers may include suitable depositionsystems including coating sources, power sources, individual pressurecontrols, deposition control systems, and temperature control. Accordingto typical implementations, the chambers are provided with individualgas supplies. The chambers are typically separated from each other forproviding a good gas separation. The flexible substrate coatingapparatus 1100 according to implementations described herein is notlimited in the number of deposition chambers. For example, but notlimited to, flexible substrate coating apparatus 1100 may include 3, 6,or 12 processing chambers.

The processing chambers 1110-1140 typically include one or moredeposition units 1112, 1122, 1132, and 1142. Generally, the one or moredeposition units as described herein can be selected from the group of aCVD source, a PECVD source, and a PVD source. The one or more depositionunits can include an evaporation source, a sputter source, such as, amagnetron sputter source, a DC sputter source, an AC sputter source, apulsed sputter source, a radio frequency (RF) sputtering source, or amiddle frequency (MF) sputtering source. For instance, MF sputteringwith frequencies in the range of 5 kHz to 100 kHz, for example, 30 kHzto 50 kHz, can be provided. The one or more deposition units can includean evaporation source. In one implementation, the evaporation source isa thermal evaporation source or an electron beam evaporation source. Inone implementation, the evaporation source is a lithium (Li) source.Further, the evaporation source may also be an alloy of two or moremetals. The material to be deposited (e.g., lithium) can be provided ina crucible. The lithium can, for example, be evaporated by thermalevaporation techniques or by electron beam evaporation techniques.

In some implementations, any of the processing chambers 1110-1140 of theflexible substrate coating apparatus 1100 may be configured forperforming deposition by sputtering, such as magnetron sputtering. Asused herein, “magnetron sputtering” refers to sputtering performed usinga magnet assembly, that is, a unit capable of a generating a magneticfield. Typically, such a magnet assembly includes a permanent magnet.This permanent magnet is typically arranged within a rotatable target orcoupled to a planar target in a manner such that the free electrons aretrapped within the generated magnetic field generated below therotatable target surface. Such a magnet assembly may also be arrangedcoupled to a planar cathode.

Magnetron sputtering may also be realized by a double magnetron cathode,such as, but not limited to, a TwinMag™ cathode assembly. In someimplementations, the cathodes in the processing chamber may beinterchangeable. Thus, a modular design of the apparatus is providedwhich facilitates optimizing the apparatus for particular manufacturingprocesses. In some implementations, the number of cathodes in a chamberfor sputtering deposition is chosen for optimizing an optimalproductivity of the flexible substrate coating apparatus 1100.

In some implementations, one or some of the processing chambers1110-1140 may be configured for performing sputtering without amagnetron assembly. In some implementations, one or some of the chambersmay be configured for performing deposition by other methods, such as,but not limited to, chemical vapor deposition, atomic laser depositionor pulsed laser deposition. In some implementations, one or some of thechambers may be configured for performing a plasma treatment process,such as a plasma oxidation or plasma nitridation process.

In certain implementations, the processing chambers 1110-1140 areconfigured to process both sides of the continuous sheet of material1150. Although the flexible substrate coating apparatus 1100 isconfigured to process the continuous sheet of material 1150, which ishorizontally oriented, the flexible substrate coating apparatus 1100 maybe configured to process substrates positioned in differentorientations, for example, the continuous sheet of material 1150 may bevertically oriented. In certain implementations, the continuous sheet ofmaterial 1150 is a flexible conductive substrate. In certainimplementations, the continuous sheet of material 1150 includes aconductive substrate with one or more layers formed thereon. In certainimplementations, the conductive substrate is a copper substrate.

In certain implementations, the flexible substrate coating apparatus1100 comprises a transfer mechanism 1152. The transfer mechanism 1152may comprise any transfer mechanism capable of moving the continuoussheet of material 1150 through the processing region of the processingchambers 1110-1140. The transfer mechanism 1152 may comprise a commontransport architecture. The common transport architecture may comprise areel-to-reel system with a common take-up-reel 1154 positioned in thewinding module 1106, the coating drum 1155 positioned in the processingmodule 1104, and a feed reel 1156 positioned in the unwinding module1102. The take-up reel 1154, the coating drum 1155, and the feed reel1156 may be individually heated. The take-up reel 1154, the coating drum1155 and the feed reel 1156 may be individually heated using an internalheat source positioned within each reel or an external heat source. Thecommon transport architecture may further comprise one or more auxiliarytransfer reels 1153 a, 1153 b positioned between the take-up reel 1154,the coating drum 1155, and the feed reel 1156. Although the flexiblesubstrate coating apparatus 1100 is depicted as having a singleprocessing region, in certain implementations, it may be advantageous tohave separated or discrete processing regions for each individualprocessing chamber 1110-1140. For implementations having discreteprocessing regions, modules, or chambers, the common transportarchitecture may be a reel-to-reel system where each chamber orprocessing region has an individual take-up-reel and feed reel and oneor more optional intermediate transfer reels positioned between thetake-up reel and the feed reel.

The flexible substrate coating apparatus 1100 may comprise the feed reel1156 and the take-up reel 1154 for moving the continuous sheet ofmaterial 1150 through the different processing chambers 1110-1140. Inone implementation, the first processing chamber 1110 and the secondprocessing chamber 1120 are each configured to deposit a portion of alithium metal film. The third processing chamber 1130 is configured todeposit a chalcogenide film. The fourth processing chamber 1140 isconfigured to deposit a lithium oxide or lithium fluoride film over thechalcogenide film. In another implementation where the continuous sheetof material 1150 is a polymer material, the first processing chamber1110 is configured to deposit a copper film on the polymer material. Thesecond processing chamber 1120 and the third processing chamber 1130 areeach configured to deposit a portion of a lithium metal film. The fourthprocessing chamber 1140 is configured to deposit a chalcogenide film. Insome implementations, the finished negative electrode will not becollected on the take-up reel 1154 as shown in the figures, but may godirectly for integration with the separator and positive electrodes,etc., to form battery cells.

In one implementation, processing chambers 1110-1120 are configured fordepositing a thin film of lithium metal on the continuous sheet ofmaterial 1150. Any suitable lithium deposition process for depositingthin films of lithium metal may be used to deposit the thin film oflithium metal. Deposition of the thin film of lithium metal may be byPVD processes, such as evaporation, a slot-die process, a transferprocess, a lamination process or a three-dimensional lithium printingprocess. The chambers for depositing the thin film of lithium metal mayinclude a PVD system, such as an electron-beam evaporator, a thin filmtransfer system (including large area pattern printing systems such asgravure printing systems), a lamination system, or a slot-die depositionsystem.

In one implementation, the third processing chamber 1130 is configuredfor depositing a chalcogenide film on the lithium metal film. Thechalcogenide film may be deposited using a PVD sputtering technique asdescribed herein. In one implementation, the fourth processing chamber1140 is configured for forming a lithium oxide film or a lithiumfluoride film on the chalcogenide film. Any suitable lithium depositionprocess for depositing thin films of lithium metal may be used todeposit the thin film of lithium metal. Deposition of the thin film oflithium metal may be by PVD processes, such as evaporation, a slot-dieprocess, a transfer process, a lamination process or a three-dimensionallithium printing process. In one implementation, the fourth processingchamber 1140 is an evaporation chamber or PVD chamber configured todeposit a lithium fluoride film or lithium oxide film over thecontinuous sheet of material 1150. In one implementation, theevaporation chamber has a processing region that is shown to comprise anevaporation source that may be placed in a crucible, which may be athermal evaporator or an electron beam evaporator (cold) in a vacuumenvironment, for example.

In operation, the continuous sheet of material 1150 is unwound from thefeed reel 1156 as indicated by the substrate movement direction shown byarrow 1108. The continuous sheet of material 1150 may be guided via oneor more auxiliary transfer reels 1153 a, 1153 b. It is also possiblethat the continuous sheet of material 1150 is guided by one or moresubstrate guide control units (not shown) that shall control the properrun of the flexible substrate, for instance, by fine adjusting theorientation of the flexible substrate.

After uncoiling from the feed reel 1156 and running over the auxiliarytransfer reel 1153 a, the continuous sheet of material 1150 is thenmoved through the deposition areas provided at the coating drum 1155 andcorresponding to positions of the deposition units 1112, 1122, 1132, and1142. During operation, the coating drum 1155 rotates around axis 1151such that the flexible substrate moves in the direction of arrow 1108.

Examples

The following non-limiting examples are provided to further illustrateimplementations described herein. However, the examples are not intendedto be all inclusive and are not intended to limit the scope of theimplementations described herein.

Lithium samples were cut into 1.0 cm² discs and polished with astainless steel brush inside an Argon glove box. This was followed bypressing the lithium with polypropylene to get a fine metallic lusterfoil. Lithium foils having a thickness of about 160 μm were placed on astainless steel spacer and transferred to a PVD deposition chamber usinga transfer vessel. The target in the PVD deposition chamber was n-typewith the composition of 38.6% Bi, 55.1% Te. The PVD deposition chamberwas filled with argon and a continuous argon flow of about 150 sccm wasestablished. The deposition time was approximately 90 seconds. A processpressure of approximately 25 mTorr was established within the PVDdeposition chamber. A deposition temperature of approximately 120degrees Celsius was established in the PVD deposition chamber. Adeposition power of 2 kW (for 86.5 Å/second) was used. A spacing ofabout 57 millimeters was established between the target and the lithiumsample. After completion of the Bi₂Te₃ deposition process, the sampleswere transferred to an argon glove box for further studies. Thethickness of the Bi₂Te₃ films deposited varied from about 50 to 200nanometers. Coin cells including the lithium and Bi₂Te₃ films wereassembled and subjected to testing.

FIGS. 12A-12D are plots depicting cell voltage changes versus time for asymmetric lithium cell (1 hour cycle) at a current density of 0.25mA/cm². The Li/Li symmetric cell studies are excellent to investigatethe reversibility of Li anode. FIG. 11A illustrates the cellarrangements of a control cell. The control cell is a Li∥Li symmetricalcell with bare lithium foil as the electrode while FIGS. 12B-Dillustrate a Bi₂Te₃ protected cell employing the lithium foil coveredwith few nanometers of Bi₂Te₃ on its top as the electrode(Li|Bi₂Te₃∥Bi₂Te₃|Li). A standard electrolyte which contained 1M LiPF₆in EC/DEC solvent (volume ratio=1:1) was used. The symmetric cells withthe standard electrolyte were assembled as a 2032-type coin cell andwere cycled at current densities of 0.250 mA/cm² and 3 mA/cm². Ascycling proceeds, lithium plating and stripping continuously change thesurface of lithium. It is noted from FIG. 12A and FIG. 12B that thefresh protected cell exhibited higher impedance due to the insulatingnature of Bi₂Te₃, however after the formation cycle the impedance wasreduced and outperformed control cells in performance.

FIGS. 13A-13B are plots of impedance spectra for Li/Li symmetric cellsusing Bi₂Te₃ modified interface and unmodified lithium control.Impedance spectra for the Li//Li symmetric cells using Bi₂Te₃ modifiedinterface as shown by trace 1310 and control unmodified lithium as shownby trace 1320. The interface resistance as shown by trace 1330 reduceddramatically after 300 hours of cycling with the Bi₂Te₃ modifiedinterface as shown by trace 1340.

FIG. 14 is a plot depicting a comparison of voltage drop for a controlsamples versus a Bi₂Te₃ modified interface as shown in examples 1 to 3after 100 hours polarization at current densities of 0.250 mA/cm², asshown by points 1410 a-d and 3 mA/cm², as shown by points 1420 a-d. Incomparison, the Bi₂Te₃ protected cell shows a stable cycling ability for400 hours and a low polarization (≈150 mV) at the same current density(FIGS. 12B and 12C). Thus, the superior cyclability of the protectedcell implies a homogeneous lithium deposit and less consumption of bothlithium and electrolyte occurring in the cell. The stable cyclabilitydemonstrates the effectiveness of Bi₂Te₃ in improving and limitinglithium dendrite formation and enhancing the reversibility.

FIG. 15A is a SEM image of lithium control cell. FIG. 15B is a SEM imageof a Bi₂Te₃ protected cell. The morphologies of the lithium metalelectrode surface from galvanostatic cycling measurements were analyzedby scanning electron microscopy. FIGS. 15A and 15B illustrate thelithium surface after cycling for 50 charge/discharge cycles in 1M LiPF₆(EC: DEC 2% FEC). The lithium electrode contact with the control lithiummetal forms needle-like nanostructures, as shown in FIG. 15A, while thelithium surface in contact with the Bi₂Te₃ film, as shown in FIG. 15B,forms a dense uniform electrodeposit. These results demonstrate that thevoltage instabilities observed in FIG. 12A and the improved stabilitydirectly results from the interface modifications of Bi₂Te₃.

FIGS. 16A-16B are plots depicting discharge capacity versus cycle numberfor a bare lithium metal anode and a lithium metal anode protected withBi₂Te₃. Li/LiCoO₂ CR2032 coin cells with Bi₂Te₃ modified Li asproof-of-concept platform to test the efficacy of the anode passivationprocedure described herein. Full cells were made with Li metal as anodeand commercial Lithium Cobalt oxide as the cathode with 1M LiPF₆ (EC:DEC 2% FEC) electrolytes. It was observed from FIG. 16A that cellscontaining 50-100 nm Bi₂Te₃ on a lithium surface provide improvedcapacity retention for at least 30 charge-discharge cycles at a highcurrent density of 3 mA/cm². Protection of the lithium metal with Bi₂Te₃not only prevents this self-discharge during the rest period before webegin electrochemical cycling but also prevents the capacity loss duringthe first 10 cycles, with the capacity of cells using Bi₂Te₃-protectedanodes falling a negligible amount from ˜3.5 mAh/cm² as shown in FIG.16B. After 30 cycles, cells with bare Li metal anodes lost their initialcapacity more predominantly, while cells with protected Li metal anodeshad a marginal loss.

To evaluate the rate capabilities of the control example and Bi₂Te₃coated samples, electrodes were subjected to charge-discharge cyclingwith different currents and the discharge capacity values are shown inFIG. 17 and FIG. 18. FIG. 19 is a plot comparing the percentage ofdischarge capacity retention at different discharge rates. FIG. 20 is aplot comparing charge rate capacity variations versus C rate. It is seenthat the discharge capacity retention of the material remains verystable and gives 95% capacity retention at 1 C discharge rates for thecomparative example. To further illustrate, a comparison of chargecapacity retention is plotted. In this example, lithium is deposited ontop of the modified interface. It is shown that Bi₂Te₃ coating of theelectrodes has positive impact on retention, 80% capacity retention atC/10, C/5, C/2, 1C, and 2C rates when compared with the control example.This further illustrates the advantage of Bi₂Te₃ coating on Li metal.

In summary, the some implementations of the present disclosure providemethods for constructing a stable and efficient SEI film includingchalcogenide materials and devices incorporating the SEI film. The SEIfilm is formed in the energy storage device during fabrication (e.g.,ex-situ) of the energy storage device. It has been found by theinventors that inclusion of chalcogenide materials in the SEI film helpsinhibit lithium dendrite growth. Not to be bound by theory but it isbelieved that inhibition of the lithium dendrite growth helps achievesuperior lithium metal cycling performance relative to current lithiumbased anodes, which rely on an in-situ SEI film formed mostly duringfirst charge of the energy storage device.

When introducing elements of the present disclosure or exemplary aspectsor implementation(s) thereof, the articles “a,” “an,” “the” and “said”are intended to mean that there are one or more of the elements.

The terms “comprising,” “including” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method, comprising: forming a lithium metal film on an anode film, wherein the anode film is formed on a current collector comprising a copper film; and forming solid electrolyte interface (SEI) film stack on the lithium metal film, comprising: forming a chalcogenide film on the lithium metal film, wherein the chalcogenide film is selected from the group of bismuth chalcogenide, a copper chalcogenide, or combinations thereof.
 2. The method of claim 1, wherein the anode film comprises graphite.
 3. The method of claim 1, wherein forming the lithium metal film comprises an evaporation process, a sputtering process, a gravure printing system, a slot-die process, or a three-dimensional lithium printing process.
 4. The method of claim 1, wherein the SEI film stack further comprises at least one of a lithium fluoride (LiF) film, a lithium carbonate (Li₂CO₃) film, a lithium oxide film, a lithium nitride (Li₃N) film, or combinations thereof.
 5. The method of claim 4, wherein the current collector has a thickness between about 2 micrometers and about 8 micrometers.
 6. The method of claim 1, wherein the current collector comprises: a first nickel or chromium containing film; the copper film formed on the first nickel or chromium containing film and having a thickness between about 50 nanometers and about 500 nanometers; and a second nickel or chromium containing film formed on the copper film and having a thickness between about 20 nanometers and about 50 nanometers.
 7. The method of claim 1, wherein the current collector comprises: a polyethylene terephthalate (PET) polymer substrate; and the copper film formed on the PET polymer substrate, wherein the copper film is deposited via a physical vapor deposition process.
 8. The method of claim 1, wherein the current collector comprising the copper film is exposed to a plasma treatment or corona discharge process to remove organic materials from exposed surfaces of the current collector.
 9. The method of claim 1, wherein the SEI film stack further comprises lithium fluoride formed on the chalcogenide film.
 10. The method of claim 1, wherein the chalcogenide film is selected from the group of CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, Bi₂Se₃, or combinations thereof.
 11. The method of claim 1, wherein the SEI film stack further comprises a lithium oxide film formed on the chalcogenide film.
 12. The method of claim 11, wherein the SEI film stack further comprises a lithium carbonate film formed on the lithium oxide film.
 13. The method of claim 1, wherein the chalcogenide film is deposited using a physical vapor deposition (PVD) process having an RF power source or a DC power source coupled to a target composed of the materials of the chalcogenide film.
 14. The method of claim 13, further comprising: forming a lithium oxide film on the chalcogenide film by depositing an additional lithium metal film via a PVD process performed in an oxygen-containing atmosphere.
 15. An anode electrode structure, comprising: a current collector comprising a copper film; an anode film formed on the current collector; a lithium metal film formed on the anode film; and a solid electrolyte interface (SEI) film stack formed on the lithium metal film, comprising: a lithium oxide film; a lithium carbonate film formed on the lithium oxide film; and a chalcogenide film formed on the lithium carbonate film, wherein the chalcogenide film is selected from the group of a bismuth chalcogenide, a copper chalcogenide, or combinations thereof.
 16. The anode electrode structure of claim 15, wherein the SEI film stack further comprises a lithium nitride film formed between the lithium metal film and the lithium oxide film.
 17. The anode electrode structure of claim 15, wherein the chalcogenide film is selected from the group of CuS, Cu₂Se, Cu₂S, Cu₂Te, CuTe, Bi₂Te₃, Bi₂Se₃, or combinations thereof.
 18. The anode electrode structure of claim 15, wherein the chalcogenide film is Bi₂Te₃.
 19. The anode electrode structure of claim 17, wherein the chalcogenide film has a thickness between about 1 nanometer to about 400 nanometers.
 20. The anode electrode structure of claim 19, wherein the lithium metal film has a thickness between about 1 micrometers and about 20 micrometers. 